Power steering pump



Oct. 31, 1967 GRENIER 3,349,714

POWER STEERING PUMP Filed Oct. 11, 1965 2 Sheets-Sheet 1 5114/1. E I? GREN/ ER INVENTOR ATTORN EYS Oct. 31, 1967 Filed Oct. 11, was

' POWER STEERING PUMP F. GRENEEH 3,349,714

2 Sheets-$119M 2 F/ay E J OOORRM- FLOW EMILE P. G REN/E/P INVENTQR TTo EYS United States Patent 3,349,714 POWER STEERING PUMP Emile P. Grenier, Ann Arbor, Mich, assignor to Ford Motor Company, Dearborn, Mich, a corporation of Delaware Filed Oct. 11, 1965, Ser. No. 494,437 6 Claims. (Cl. 10341) This invention relates to a positive displacement type fluid pump that may be employed in a power steering system and more particularly to such a positive displace ment type pump embodying a novel output volume or flow control regulator.

In power steering systems positive displacement pumps are ordinarily employed for supplying fluid under pressure to the power steering motive device and the pump is driven from the vehicle engine and accordingly is operated over a widely varying speed.

In a positive displacement pump the output volume of the pump will increase proportionally as the speed of the pump increases unless a flow control means is employed to limit the flow of the pump at higher speeds. In conventional power steering pumps a flow control valve has been employed that is positioned between the discharge port of the pump and the inlet port of the pump.

This flow control valve has means associated with it for sensing the flow as it increases with increasing pump speeds and this ordinarily takes the form of an orifice positioned between the discharge port of the pump and the outlet to the power steering device. The fluid after it passes through the orifice is applied to one end of the flow control valve and this same end ordinarily is spring urged in such a direction as to cut off communication between the discharge port of the pump and the inlet port. When the pressure drop across the orifice reaches a certain predetermined level the force applied to the end of the valve adjacent the discharge port of the pump becomes greater than the force applied by the pressure of the fluid on the other side of the orifice and the force of the spring. This moves the flow control valve into position where a portion of the fluid discharged from the discharge port of the pump is bypassed or discharged into the inlet port.

In the ordinary power steering pump. the action described above will provide, after a certain predetermined speed of the pump has been reached, a constant flow to the power steering device. It has been found that this type of flow control arrangement while satisfactory in certain applications has some definite disadvantages, for example, it may cause excessive heat buildups and high fluid temperatures as well as undesirable high power requirements for the pump.

The present invention remedies these disadvantages and provides an eminently satisfactory power steering pump by reducing the pump flow at engine or pump speeds above a predetermined level. This is done by providing the orifice described above with means for varying its eifective area in accordance with the position of the flow control valve. This may be accomplished by means of a variable area metering rod or pin that is in effective engagement with an aperture thereby forming a variable area orifice. The area of the orifice is varied by the movement of the flow control valve and as the pump operates at progressively higher speeds the flow control valve will vary the position of the metering rod with respect to the aperture such that the higher cross-sectional area of the metering rod is in eflective relationship with the orifice to effectively reduce the area of the orifice.

This action increases the pressure differential between the end of the flow control Valve position adjacent the outlet or discharge port of the pump and the other end which is subjected to the spring pressure and the pressure of the fluid after it is passed through the variable orifice. As a result the flow control valve will move into a new position in which a greater quantity of fluid. from the output port is bypassed into the inlet port and a smaller quantity flows to the outlet of the power steering pump and to the power steering device coupled to this outlet.

In the prefered form of the invention, the metering rod has two sections of constant cross-sectional area, with one section having a lower cross-sectional area than the other. These two sections are intercoupled by a tapered section. When the speed of the pump is below a predetermined level the smaller section is in eflective relationship with the aperture thereby creating an orifice having a certain crosssectional area. This first section remains in effective posi' tion with respect to the aperture until a first predetermined speed level of the pump is reached. The tapered section moves into effective relationship with the aperture therebetween this first predetermined speed level and a second higher predetermined speed level. At speeds of the pump higher than the second predetermined speed level the second section of higher cross-sectional area comes into effective relationship with the aperture to provide an orifice having a constant but smaller cross-sectional area for speeds above the second predetermined speed level.

The above-described action reduces the pump flow at speeds above the first predetermined speed level in a substantially straight line relationship in which the flow decreases gradually as the speed of the pump increases. At speeds higher than the second predetermined speed level the output volume of the pump again becomes a constant due to the above-describedaction of the metering pin with respect to the aperture.

An object of the present invention is the provision of a constant displacement rotary type pump in which a novel flow control means is provided to reduce the pump flow when the speed of the pump reaches a predetermined level.

A further object of the invention is the provision of a power steering pump of the positive displacement type in which the flow of the pump is reduced at higher speed levels thereby reducing the power requirements for the pump and reducing the temperature of the fluid being pumped.

Another object of the invention is the provision of a power steering pump of the positive displacement type employing a novel flow control means that provides a constant flow for a certain speed range of the pump and provides lower constant flow at a higher speed range of the pump.

Other objects and attendant advantages. of the present invention may be more readily realized when the specification is considered in connection with the attached drawings, in which:

FIGURE 1 is a sectional view of the power pump of the present invention;

FIGURE 2 is a partial sectional view taken along the lines 22 of FIGURE 1;

FIGURE 3 is a partial sectional view taken along the lines 33 of FIGURE 1;

FIGURE 4 is a partial sectional view taken along the lines 4-4 of FIGURE 1;

FIGURE 5 is a partial sectional view taken along the lines 5-5 of FIGURE 1;

FIGURE 6 is a partial sectional view taken along the lines 6 -6 of FIGURE 1;

FIGURE 7 is a partial sectional view through the pump showing a dowel pin arrangement for holding various sections of the pump together;

FIGURE 8 is a partial sectional view through the pump showing a spring for biasing the various sections of the housing together; and

FIGURE 9 is a curve showing the output flow of the pump as a function of pump speed.

Referring now to FIGURE 1 there is shown pump 10 of the positive displacement type that includes a housing 11 having a rotatable shaft 12 mounted therein by means of a bushing 13. A reservoir 14 in the form of a sheet metal can completely surrounds the periphery of the housing 11 and is sealed thereto by means of an O-ring 15. The reservoir has an inlet 16 from an external device utilizing hydraulic fluid, for example, a power steering mechanism, and a filler cap 17 for filling the reservoir 14 with hydraulic fluid.

The pumping mechanism of the pump 10 is mounted within a chamber 21 formed in the housing 11. A pair of dowels, one of which is shown in elevation in FIGURE 7 and which are designated by the numerals 23 and 24, are anchored within the housing 11 and extend through the chamber 21. These dowels carry and support the pumping mechanism. This pumping mechanism comprises a lower pressure plate 26 as can most readily be seen by reference to FIGURE 6. Mounted on the top of the lower pressure plate 26 is a pumping element cartridge generally designated by the numeral 27 in FIGURE 5. This pumping element cartridge comprises a cam insert 28 and a rotor 31. The rotor carries a plurality of pumping slippers 32 each of which is U-shaped in cross-section and is open at each end to provide two sealing surfaces on each slipper.

An upper pressure plate 34 is positioned above the pumping element cartridge 27. This upper pressure plate shown in detail in FIGURE 4 is similar to the lower pressure plate 26. A separator plate 35 shown in FIGURE 3 is positioned above the upper pressure plate 34 and a valve plate 36 shown in detail in FIGURE 2 is positioned over the separator plate 35 and is sealed to the housing 11 by means of an O-ring seal 37 best shown in FIG- URE 1. An end cap 38 fits over the valve plate 36 and engages a shoulder in the housing. The end cap 38 is retained in the housing by means of a lock ring 39 and is sealed thereto by means of an O-ring seal 41.

Spring means that take the form of a pair of springs, one of which is shown at 43 in FIGURE 8, urge the valve plate 36, the separator plate 35, the upper pressure plate 34, the pumping element cartridge 27 and the lower pressure plate 26 into sealing engagement to prevent leakage between the rotor and the upper and lower pressure plates.

The valve plate 36 houses a flow control valve generally designated by the numeral 45. The flow control valve 45 comprises a valve spool or cylindrical valve member 46 that is biased toward a closed position by a spring 47 positioned within the cylindrical chamber 48 that houses the valve spool or cylindrical valve member 46.

The flow control valve 45 also includes a pressure relief valve that has a ball 51 biased into engagement with an orifice in a relief plug 52 by means of a spring 53. An orifice 54 is provided in the valve spool or cylindrical valve member 46 for permitting flow from the interior to the exterior thereof when the pressure of the fluid forces the ball 51 from its seat 52 under extremely high pressures.

The end cap 38 is provided with a fitting 56 that serves together with the fitting 57 attached to the sheet metal can forming reservoir 14 as an outlet for the power steering pump. This outlet is adapted to be connected to a power steering device such that fluid under pressure from the outlet powers this device and provides the energy necessary for operating a power steering system.

Fluid is pumped from the reservoir 14 defined by the sheet metal can through an oblong aperture generally designated by the numeral 61. This aperture is in alignment with the inlet passage 63 in valve plate 36 as shown in FIGURE 2. From there the fluid is pumped through the bypass passage 64 in the valve plate and then through the bypass grooves 65, 66 and 67, in the separator plate 35, the upper pressure plate 34 and the cam insert 28, respectively. This provides intake fluid in the space between the housing 11 and the stack of pump elements including the umping element cartridge 27, the upper and lower pressure plates 26 and 34, and the separator plate 35.

This intake fluid is in communication with the pumping elements of the pump including the rotor 31 and the slipper elements 32 through the inlet ports or grooves 71 and 72 located in each of the lower and upper pressure plates 26 and 34. The fluid is pumped from the inlet ports 71 and 72 to the outlet ports 73 and 74 located in both the upper and lower pressure plates. Fluid received in the inlet port 71 of the upper and lower pressure plates is delivered under pressure to the outlet port 73 in the upper and lower plates and fluid received in the inlet port 72 of the upper and lower pressure plates is delivered under pressure to the outlet port 74 in the upper and lower pressure plates.

The outlet ports 74 in the upper and lower pressure plates are connected by means of a bore 75 positioned in the cam insert 27 while the outlet ports 74 in the upper and lower pressure plates are connected by a bore 76 in' the cam insert 27. The outlet ports 74 and 73 in the upper pressure plate 34 are in communication with circular apertures 81 and 82 respectively in the separator plate 35.

Means are also provided to supply fluid to the volume behind the slippers 32. This takes the form of small inlet ports 83 and 84 in the upper and lower pressure plates. The fluid is discharged from these volumes into small outlet ports 85 and 86 in the upper and lower pressure plates. The small outlet ports 85 and 86 are in communication with the outlet ports 73 and 74 in the lower pressure plate 26 and the small outlet ports 85 and 86 in the upper pressure plate 34 are in communication with the circular apertures 81 and 82 in the separator plate 35.

As fluid under pressure is delivered into the two circular apertures 81 and 82 of the separator plate 36 it finds its way into the pressure port 91 in the valve plate 36 as shown in FIGURE 2. The fluid under pressure is then delivered to a chamber 92 through a discharge port 93 formed in the valve plate 36. The chamber 92 is defined by the cylindrical bore or chamber 48 in the valve plate, by the end of the valve spool or cylindrical valve member 46 and by an end wall member 94 that is juxtaposed with relationship to the end 95 of the valve spool or cylindrical valve member 46. An aperture 96 is positioned in the end wall member 94 and it connects the chamber 92 with a chamber 98 formed or defined by the valve plate 36 and the end cap 38. This aperture causes a pressure drop so that hydraulic fluid in the chamber 98 is at a lower pressure than the fluid in chamber 92. The fluid in the chamber 98 is then delivered to the outlet of the pump defined by the fittings 56 and 57 as previously noted.

A metering rod or pin 101 actuated or carried by the valve spool or cylindrical valve member 46, is employed in conjunction with the aperture 96 to form a variable area orifice. This metering rod or pin 101 includes a first or central area 102 having a constant cross-sectional area and a second or end section 103 having a larger constant cross-sectional area. The two sections 102 and 103 are interconnected by a tapered section 104.

Fluid under pressure in the chamber 98 also flows through an orifice or opening 105 in the valve plate 36 to pressurize the end 106 of the valve spool or cylindrical valve member 46 that is remote from the chamber 92. The areas of the ends of the valve spool or cylindrical valve member 46 may be substantially equal so that the end 95 of the valve spool or cylindrical valve member 46 in the chamber 92 is subjected to the outlet pressure of the pump while the end 106 of the valve spool or cylindrical valve member 46 adjacent the opening 105 is subjected to the lesser pressure due to the pressure drop across the variable orifice that is defined by the aperture 96 in the member 94 and the metering rod or pin 101. When the flow of fluid reaches a certain desired magnitude at a certain predetermined speed of the pump, the pressure differential just described overcomes the force exerted by the valve spring 47 and causes the valve spool or cylindrical valve member 46 to shift so as to provide communication between the chamber 92 and a bypass port 106 in the valve plate 36. This bypass port 106 is in communication with the bypass passage 64 position in the valve plate member 36.

When the pump is at rest the spring 47 will force the valve spool or cylindrical valve member 46 into engagement with the end wall member 94 that carries the aperture 95 and hence the smaller cross-sectional area section 102 of the metering pin 101 will be in effective position with respect to the aperture 96. In this position, the valve spool or cylindrical valve member 46 will prevent communication between the chamber 92 and the bypass port 106 and as the speed of the pump increases, flow of the hydraulic fluid from the pump outlet at the fittings 56 and 57 will increase as a substantially linear function of the speed of rotation of the rotor of the pump, since the pump is a constant displacement pump. This linear increase is shown on the curve of FIGURE 9.

When the speed of the pump reaches a predetermined speed and the flow reaches a given rate the differential force on force valve member 46 due to the pressure differential between the fluid in the chamber 92 acting on one end of the valve and the fluid in the chamber that houses the spring 47 in the other end reaches a point where the valve spool 46 or cylindrical valve member is moved to provide communication between the chamber 92 and the bypass port 106. This dumps a portion of the fluid from the discharge port of the pump as at 93 into the bypass port 106 and therefore bypasses a portion of the fluid pumped. As a result the flow of the pump will remain at a substantially constant level as long as section 102 of the metering pin 101 remains in effective relationship with aperture 96, since the area of the orifice defined by aperture 96 and section 102 of the metering pin 101 remains constant under these conditions.

When the speed of the pump, however, reaches a certain predetermined level the tapered section 104 of the metering rod or pin 101 moves into effective engagement with the aperture 96 and the flow of the pump drops 01f as shown on the curve since as the tapered portion is encountered the pressure differential increases due to the decrease in the effective area of the orifice and this dropping off will occur in a substantially linear fashion until another higher predetermined pump speed is reached. At this time the larger cross-sectional area portion 103 of the metering rod or pin 101 will be effective to further reduce the effective area of this orifice. The area of the section 103 is constant for a considerable portion of the axial length of the metering pin 103 and as a result the flow of the pump will remain at a constant value for speed above this second predetermined higher speed.

Thus, at higher pump speeds the flow of fluid from the pump that is available at the outlet of the pump will be reduced, and preferably will be reduced to a lower constant value. This lowers the temperature of the oil from the temperature that would prevail had the flow remained constant at the higher level shown on the curve and it also reduces the amount of power needed to drive the pump. Both of these are significant advantages in a power steering system since the lower temperature of the oil or hydraulic fluid aids in preventing sticking of the valves in the power steering system that might otherwise occur due to the higher temperatures and further, the lowering of the power requirements necessary to drive the pump has a distinct advantage in permitting this power to be utilized in doing other eflective work.

What I claim and desire to Letters Patent is:

1. A power steering pump of the constant displacement type comprising a pump chamber having inlet and discharge ports, a rotor operable in said pumping chamber for pumping fluid between said inlet and discharge ports, a valve chamber positioned between said inlet and discharge ports and having an opening connecting said inlet and discharge ports, a valve member positioned in said valve member positioned in said valve chamber, spring means positioned in said valve chamber and'engaging one end of said valve member for urging said valve member into a position to close said opening, an outlet orifice positioned adjacent the other end of said valve and having one side in communication with said one end of said valve member and adapted to be coupled to a power steering mechanism, said outlet orifice having the other side positioned in communication with said discharge port of said pump, and means operable by the movement of said valve member for reducing the effective area of said orifice when the speed of the rotor exceeds a predetermined level.

2. In a rotary pump, a housing having a rotor chamber positioned therein and an intake port and a discharge port communicating with the rotor chamber at spaced points, rotor means positioned in said rotor chamber and operable tor pumping fluid from said'intake port to said discharge port, portions of said housing defining a substantially cylindrical valve chamber spanning said intake and discharge ports with said discharge port being positioned adjacent one end of said cylindrical valve chamber and with said intake port being positioned in a direction toward the other end of said cylindrical valve chamber, a cylindrical valve member positioned in said cylindrical valve chamber, spring means positioned in said cylindrical valve chamber and engaging said cylindrical valve member for urging said cylindrical valve member in a direction toward said one end of said cylindrical valve chamber and covering said intake port, said housing including an outlet adapted to be connected to a power steering apparatus, said cylindrical valve chamber having an end wall member that together with said one end of said cylindrical valve member defines a chamber that is in communication with said discharge port, an orifice positioned in one of said members and a variable area metering rod carried by the other of said members extending through said orifice, said variable area orifice being in communication with the other end of said cylindrical valve member and with said outlet, whereby said variable area metering rod varies the effective area of said orifice as said cylindrical valve member is moved in said cylindrical valve chamber due to varying speeds and output volumes of said pump.

3. The combination of claim 2 in which said variable area metering rod has a free end portion and a central portion with the end portion having a larger cross-sectional area than said central portion and an intermediate tapered portion interconnecting said free end portion and said central portion, said central portion being positioned in said orifice when the speed of the pump is below a predetermined speed, said tapered portion being positioned in said orifice when the speed of the pump is between said predetermined speed and a higher predetermined speed and said free end portion being in position in said orifice when the speed of the pump is above said higher predetermined speed, the relative movement of said metering rod and said orifice being caused by the movement of said cylindrical valve member in said cylindrical valve chamber as the speed of the pump increases.

4. A power steering pump comprising a housing including an inlet port and discharge port and having a pumping chamber, a rotor positioned in said pumping chamber for pumping fluid from said inlet port to said discharge port, a flow control valve member positioned between said inlet and said discharge ports and having secure by United States one end positioned incommunication with said discharge port, spring means engaging the other end of said flow control valve member and urging said valve member in a direction to close communication between said inlet and said discharge ports, said housing including means forming an outlet adapted to communicate with a power steering device, fluid passage means connecting said discharge port and said one end of said valve with said outlet and said other end of said valve, and variable area orifice means positioned in said fluid passage means between said one end of said flow control valve and both said outlet and said other end of said valve and operable directly by the movement of said flow control valve for reducing the volume of fluid flowing from said outlet when the speed of the rotor exceeds a predetermined level.

5. The power steering pump of claim 4 in which said fluid passage means includes an end wall member positioned in juxtaposed relationship to said one end of said flow control valve member and said variable area orifice means includes an opening positioned in one of said members and a variable area metering rod attached to the other of said members and extending in an axial direction through said opening.

6. The combination of claim 5 in which said variable area metering rod has a first section of constant crosssectional area and a second section of constant and smaller crosssectional area and a tapered section interconnecting said first and said second sections, said second section being positioned in operative relatioinship within said aperture when the speed of said rotor is below a predetermined level, said tapered section and said aperture being brought into operative relationship by the movement of said flow control valve member when the speed of the rotor is between said predetermined level and a higher predetermined level, and said first section of said metering rod being brought into operative relationship with said aperture by the movement of said flow control valve when the speed of the rotor is above said higher predetermined level.

References Cited UNITED STATES PATENTS 2,724,335 11/1955 Eames 103-42 2,748,711 6/1956 Drude 103-42 2,977,888 4/1961 Livermore 103-42 2,982,217 5/1961 Thrap 103-42 3,160,332 12/1964 Brunson 137-117 3,200,752 8/1965 Clark et al. 103-42 3,233,651 2/ 1966 Smith 103-42 3,266,426 8/1966 Brunson 103-42 3,267,864 8/1966 Eddy 10342 DONLEY I. STOCKING, Primary Examiner.

W. J. KRAUSS, Assistant Examiner.

Disclaimer 3,349,714.Em2'l6 P. Grem'er, Ann Arbor, Mich. POWER STEERING PUMP. Patent dated Oct. 31, 1967. Disclaimer filed June 23, 1974, by the assignee, Ford Motor Company.

Hereby enters this disclaimer to claims 1 through 6 of said patent.

[Oficial Gazette August 5, 1.975.] 

1. A POWER STEERING PUMP OF THE CONSTANT DISPLACEMENT TYPE COMPRISING A PUMP CHAMBER HAVING INLET AND DISCHARGE PORTS, A ROTOR OPERABLE IN SAID PUMPING CHAMBER FOR PUMPING FLUID BETWEEN SAID INLET AND DISCHARGE PORTS, A VALVE CHAMBER POSITIONED BETWEEN SAID INLET AND DISCHARGE PORTS AND HAVING AN OPENING CONNECTING SAID INLET AND DISCHARGE PORTS, A VALVE MEMBER POSITIONED IN SAID VALVE MEMBER POSITIONED IN SAID VALVE CHAMBER, SPRING MEANS POSITIONED IN SAID VALVE CHAMBER AND ENGAGING ONE END OF SAID VALVE MEMBER FOR URGING SAID VALVE MEMBER INTO A POSITION TO CLOSE SAID OPENING, AN OUTLET ORIFICE 